Field of Invention
The present invention relates to permanent magnetic devices, and more particularly to a method and an apparatus for sintering a NdFeB rare earth permanent magnet.
Description of Related Arts
The NdFeB rare earth permanent magnetic material is increasingly applied because of its excellent magnetism, and widely applied in medical nuclear magnetic resonance imaging, computer hard disk drives, audio equipment and the mobile phones. Along with the benefits of energy-saving and low-carbon economy, the NdFeB rare earth permanent magnetic material is further applied in auto parts, household appliances, energy-saving control motors, hybrid power vehicles and wind generators.
In 1982, the Japan Sumitomo Special Metals Co., Ltd. initially published the Japanese patent applications, JP 1,622,492 and JP 2,137,496, to disclose the NdFeB rare earth permanent magnetic material, and subsequently submitted the correspondent U.S. patent application and the correspondent European patent application to disclose the features, the constituents and the preparation method thereof, wherein an Nd2Fe14B phase is confirmed as the main phase; and wherein a rich Nd phase, a rich B phase and rare earth oxide impurities are confirmed as the grain boundary phase.
On Apr. 1, 2007, the Japan Hitachi Metals is merged with the Japan Sumitomo Metals and inherited the rights and obligations licensed by the related patents of NdFeB rare earth permanent magnets of Japan Sumitomo Metals. On Aug. 17, 2012, the Japan Hitachi Metals claimed the owned U.S. patents, comprising U.S. Pat. No. 6,461,565, U.S. Pat. No. 6,491,765, U.S. Pat. No. 6,537,385 and U.S. Pat. No. 6,527,874, for the lawsuit in the United Sates International Trade Commission (ITC).
The Chinese patent CN1187152C disclosed the sintering box for sintering the rare earth permanent magnet and the Chinese patent CN1240088C disclosed the method for preparing the rare earth sintered magnet.